fix but model with slope and without level

Author: andre_ramos

Project.toml

@@ -1,7 +1,7 @@
 name = "StateSpaceLearning"
 uuid = "971c4b7c-2c4e-4bac-8525-e842df3cde7b"
 authors = ["andreramosfc <andreramosfdc@gmail.com>"]
-version = "2.0.12"
+version = "2.0.13"
 
 [deps]
 Distributions = "31c24e10-a181-5473-b8eb-7969acd0382f"

src/models/structural_model.jl

@@ -1592,7 +1592,7 @@ function simulate_states(
     end
 
     slope = ones(T, N_scenarios) .* slope
-    model.level ? trend = ones(T, N_scenarios) .* trend : nothing
+    model.level || model.slope ? trend = ones(T, N_scenarios) .* trend : nothing
     model.seasonal ? seasonals = [ones(T, N_scenarios) .* s for s in seasonals] : nothing
     for t in (T + 1):(T + steps_ahead)
         slope_t = if model.slope